Private optical insurance _exists_, but basically only as a corporate perk that pays for more expensive frames, etc. Most people wouldn't have it, and it didn't exist at all until a few years ago. Private health insurance is more common, but doesn't pay for glasses or routine eye tests.

I believe PRSI (the government social insurance scheme) pays about 30 euro for a basic eye test. At the big local chain, people without either PRSI or medical card (this would mostly be non-resident foreigners, plus maybe some early retirees etc), pay 30 euro, plus about 60 euro for basic frames with basic lenses.